The goal of the proposed research is to obtain a systematic set of data on the input-output relations among evoking stimuli and evoked oto-acoustic emissions in large numbers of normal and non-normal human ears. The proposed research will provide a systematic description of evoked oto-acoustic emissions in normal and non-normal ears and provide a basis for evaluating their clinical applicability. Evoked emissions appear to be highly tuned and subject to both forward and simultaneous masking and suppression. These characteristics of evoked emissions, together with their susceptability to metabolic and traumatic insults, and their non-linear relation to stimulus amplitude suggest that they originate within the cochlea and are highly related to both the frequency selective and non-linear processes of the cochlea. The exact site and/or mechanism of their generation, as well as their true distribution across ears and thei significance, are matters of some controversy. At least some of these controversies are due to the lack of systematic data. Despite the large numbers of papers that have appeared in the literature since Kemp's (1978) original work, relatively few conditions and subjects are actually reported. Systematic delineation of the relations between emissions evoked by different stimuli and the relations between the status of the peripheral auditory system and characteristics of evoked emissions is important if their source and significance are to be identified. The proposed research will provide a systematic description of evoked oto-acoustic emissions in normal and non-normal ears and provide a basis for evaluating their clinical applicability.